The field of art to which the claimed invention pertains is catalytic composites as well as the manufacture and use thereof. More specifically, the claimed invention relates to use of a catalytic composite comprising diatomaceous earth dispersed in a refractory metal oxide binder material There are a number of continuous cyclical processes employing fluidized solid techniques in which carbonaceous materials are deposited on the solids in the reaction zone and the solids are conveyed during the course of the cycle to another zone where carbon deposits are at least partially removed by combustion in an oxygen-containing medium. The solids from the latter zone are subsequently withdrawn and reintroduced in whole or in part to the reaction zone.
One of the more important processes of this nature is the fluid catalytic cracking (FCC) process in which heavy petroleum hydrocarbon feed stocks boiling in excess of about 400.degree. F. are converted to lower boiling hydrocarbons in the motor fuel boiling range by heating them in contact with an amorphous silica-alumina catalyst maintained in a fluidized state. The FCC process does not employ added hydrogen. While other composites comprising silica, e.g. silica-zirconia, silica-magnesia, etc., have been known to catalyze the cracking reaction, the silica-alumina composite has been by far the most widely accepted catalyst in the industry. More recently, improved catalysts having the capability of yielding greater proportions of high octane gasoline have been prepared by the inclusion of a finely divided zeolite, or crystalline aluminosilicate, either naturally occurring or synthetically prepared, within the amorphous silica-alumina matrix. Prior inventors have prepared, tested and compared hydrocarbon conversion catalysts comprising a finely divided crystalline aluminosilicate distributed in an amorphous silica matrix on the one hand, and in an amorphous silica-alumina matrix on the other hand.
The FCC reaction produces, in addition to the desirable products, such as high octane gasoline, a quantity of undesirable products such as the carbonaceous material or coke that deposits on the catalyst. The above mentioned zeolite containing catalysts enable minimization of these undesirable products while maximizing the conversion to the desirable products. Continuous efforts are being made, however, to improve the performance of even the zeolite containing catalysts.
There are many zeolite containing FCC catalysts described in the art other than those mentioned above which achieve improved performance by the addition of certain ingredients either to the catalyst itself or to the materials used in the manufacture of the catalyst at one or more of the manufacturing states. U.S. Pat. No. 4,259,212 to Gladrow et al. is an example of one such reference. None of such zeolite containing FCC catalysts, however, contains diatomaceous earth.
U.S. Pat. No. 4,233,139 to Murrell et al. does teach a hydrocarbon conversion catalyst which may contain kieselguhr (includes diatomaceous earth), but does not teach zeolite content in the catalyst and does require a supported catalytically active metal oxide comprising or mixed with an oxide of tungsten or niobium.
There are numerous teachings in the art of catalytic compositions which might contain both zeolite and diatomaceous earth, but which also contain supported catalytic metal oxides and which are for hydrogenation processes and not suitable for the fluidized catalytic cracking of hydrocarbons in the absence of hydrogen. Examples of such art are U.S. Pat. Nos. 4,218,308; 4,497,907; and European Patent Application 0 097 047.
U.S. Pat. No. 4,218,308 to Itoh et al. also requires supported catalytic metal oxides and relates only to a hydrogenation catalyst not suitable for the fluidized catalytic cracking of hydrocarbons in the absence of hydrogen.
U.S. Pat. No. 3,257,311 to Frilette et al. mentions a catalyst for the selective conversion of hydrocarbons with an aluminosilicate catalyst which might have a diatomaceous earth matrix, although it is preferred to use the aluminosilicate catalyst per se (see column 3). There is no teaching in Frilette et al. that the diatomaceous earth might actually enhance catalyst performance or improve the properties of the catalyst. There is no teaching in Frilette et al. of specific criteria for diatomaceous earth concentrations or particle size which I have found to effect surprisingly advantageous results.
U.S. Pat. No. 2,394,710 to McAfee mentions using diatomaceous earth as a "relatively inert contact material" in thermal hydrocarbon conversion processes and is clearly not even of superficial relevance to my invention.
In the Encyclopedia of Chemical Technology, Kirk-Othmer, Third Edition, Volume 7, it is mentioned that special grades of diatomite are used as a carrier for catalysts in petroleum refining.
I have discovered that diatomaceous earth incorporated into a molecular sieve type fluidized catalytic cracking process enables higher production of gasoline while minimizing the production of undesirable coke.